1. Field of the Invention
The present invention relates generally to a communication system, and in particular, to a service provision method and system for seamlessly providing a Multicast and Broadcast Service (MBS) desired by a user in a communication system supporting MBS.
2. Description of the Related Art
Intensive research in the next generation communication system is being conducted to provide users with high-speed services having various Quality of Service (QoS) classes. Particularly, research and development in the next generation communication system is being carried out to support high-speed services guaranteeing mobility and QoS for a Broadband Wireless Access (BWA) communication system.
The BWA communication system provides users with high-speed multimedia communication services. MBS provides beyond the voice and packet data communicant services provided by the existing communication system. In a communication system supporting MBS, a transmitter, or a Base Station (BS), provides broadcast content data to multiple receivers, or Mobile Stations (MSs), using a multicast scheme. The multicast scheme is a scheme in which a transmitter transmits data to multiple receivers. The communication system supporting MBS divides a broadcast service zone into multiple service zones, in each of which one or more transmitters transmit MBS to all receivers located in the corresponding service zone using the multicast scheme. Therefore, the receivers located in each service zone can simultaneously receive MBS data from the transmitter. In the communication system supporting MBS, one transmitter can take charge of more than one service zones and can simultaneously provide MBS to receivers located in the corresponding service zones. With reference to FIG. 1, a description will now be made of a general Institute of Electrical and Electronics Engineers (IEEE) 802.16 compliant communication system supporting MBS.
FIG. 1 is a schematic diagram illustrating a configuration of a general IEEE 802.16 communication system supporting MBS.
Referring to FIG. 1, the IEEE 802.16e communication system has a multi-cell configuration, i.e. has a cell #1 100 and a cell #2 150, and includes a BS1 102 and a BS2 152 in charge of their associated cells 100 and 150; an MS1 104 that is located in cell #1 100 and receives a communication service from BS1 102; an MS3 154 that is located in cell #2 150 and receives a communication service from BS2 152; and an MS2 110 that is located in the boundary between cells 100 and 150, where cell #1 100 and cell #2 150 overlap each other, and receives a communication service from BS1 102 and BS2 152. It is assumed herein that MSs of MS1 104, MS2 110 and MS3 154 have both mobility and fixability, and signal exchange between BSs 102 and 152, and MSs 104, 110 and 154 located in cells 100 and 150 is achieved using Orthogonal Frequency Division Multiplexing (OFDM)/Orthogonal Frequency Division Multiple Access (OFDMA).
As the communication system provides an MBS service to users, or MSs 104, 110 and 154, MSs 104, 110 and 154 receive MBS from BSs 102 and 152 using a single-BS access scheme or a multi-BS access scheme. More specifically, the single-BS access scheme is a scheme in which an MS receives MBS from one BS in which the MS itself is registered, and the multi-BS access scheme is a scheme in which an MS receives MBS not only from a BS in which the MS itself is registered, but also from other BSs. That is, as shown in FIG. 1, MS1 104 and MS3 154 receive MBS from their associated BS1 102 and BS2 152 in which they are registered, using the single-BS access scheme, and MS2 110 receives MBS not only from BS1 102 but also from BS2 152 using the multi-BS access scheme.
In the single-BS access scheme, to receive MBS, an MS is registered in all BSs supporting the MBS. In the multi-BS access scheme, however, a connection for MBS between a BS and an MS is generated through a Dynamic Service Addition (DSA) process, or a service allocation process, and the MS acquires the connection information with the BS by receiving Type/Length/Value (TLV) encoding information for data identification from the BS.
The MS can identify an MBS zone depending on a Connection Identifier (CID) or a Security Association (SA). The MBS zone as used herein refers to a zone where an MBS flow is available depending on the CID or the SA, i.e. a predetermined zone where the MS can receive MBS. The BS broadcasts information on the MBS zone to MSs over a Downlink Channel Descriptor (DCD) message. That is, the MBS zone can refer to a group of BSs that use the same CID or SA to provide MBS.
The MBS data to be provided to an MS is transmitted to all BSs located in an MBS zone supporting the same MBS, and the BSs transmit the MBS data to MSs according to channel information, so the MSs located in the MBS zone can receive the MBS data. To receive predetermined MBS data from the BS or to receive other MBS data while receiving the predetermined MBS data, the MS can change a Frequency Assignment (FA) of a channel allocated for transmission of the MBS data. In particular, when an arbitrary BS uses multiple FAs, because the BS does not broadcast the same MBS data at all of the FAs, the MS, to receive predetermined MBS data, should switch to a corresponding FA at which the predetermined MBS data is transmitted. For this, there is a need for inter-FA handover. That is, in the communication system supporting MBS, to seamlessly provide MBS requested by a user, there is a need for an inter-FA handover scheme for a channel allocated to provide MBS.